A number of systems for controlling exhaust emissions produced by an internal combustion engine currently exist. It is desirable with such systems to control the actual air-to-fuel ratio (A/F) of the exhaust emissions by controlling the air and/or fuel supplied to the engine to reach a targeted A/F ratio. Reaching the targeted A/F ratio will provide a number of benefits including, but not limited to, achieving a desired oxides of nitrogen (NOx) production level.